1. Field of the Invention
The present invention relates to an apparatus and a method for searching for information of cases similar to a search target medical image, and to a recording medium, in which a program causing a computer to execute the method is recorded.
2. Description of the Related Art
In order to support interpretation of medical images by physicians and diagnosis carried out by clinicians based on medical images, similar case search systems have been proposed. In such systems, medical images, information including interpretation results and diagnosis results pertinent to the images, and the like are stored in databases, and the databases are searched for images similar to medical images as targets of image interpretation/diagnosis and for information such as results of image interpretation/diagnosis pertinent to the similar images.
For example, a system is known wherein an image database storing image data sets representing images of subjects is searched for similar image data sets having regions whose pictorial characteristic is similar to an image data set inputted as a search target and a result of the search is outputted (see U.S. Patent Application Publication No. 20040003001, for example).
In addition, a similar medical image search apparatus having a similar medical image database is known (see Japanese Unexamined Patent Publication No. 2004-173748, for example). The similar medical image database relates to each other the types of operations for judgment processing used at the time of detection of shadows of foci included in medical images, a characteristic quantity of the shadows of foci found in the judgment processing, and the medical images. The similar medical image search apparatus searches the similar medical image database based on a result of the same judgment processing carried out on one of a plurality of interpretation target images.
In medical imaging, lesions are identified in many cases by obtaining temporal change images of the same body part associated with infusion of a contrast material, that is, images at different times. For example, in the case of examination to identify a liver tumor by use of CT, difference in spread of a contrast material is observed between images of four temporal changes comprising a pre-contrast phase image (plain CT), an early phase image (an arterial phase image), a portal phase image (a portal venous phase image), and a late phase image (an equilibrium phase image), and judgment is made on distinction between veins and the tumor and on progress of the disease.
A region of liver tumor has small differences in CT values from other normal liver regions. In addition, the region in an image obtained at a single time phase is sometimes extracted as a region similar to surrounding veins, depending on how a contrast material has spread. Therefore, a plurality of images at different time phases need to be obtained for comparison of complex changes associated with temporal changes in an amount of absorbed X rays, that is, complex changes in CT values with time.
In the case where the similar case search system or the like described in U.S. Patent Application Publication No. 20040003001 or Japanese Unexamined Patent Publication No. 2004-173748 is applied to identification of such a liver tumor, not all temporal change images described above are used, since the system searches for similar cases by using only one image as a search target.
Furthermore, the system does not maximally use information obtained in examinations, and whether images to be compared to each other were obtained at the same time phase has not been considered.